July / August 2007
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DEICING SALTS SPELL TROUBLE FOR TREES
When winter storms are in full force, many are turning to salt deicers as a safety measure against ice on roads and sidewalks. While salt stains are a common sight on cars and steps, many may not know that salt deicing products can also damage foliage on trees.
Sodium chloride, the scientific name for rock salt, is the most popular and generally least costly type of deicer. “Unfortunately, as ice and snow treated with rock salt melts, the resulting runoff may cause harmful by-products to seep into soil or splash onto leaves, causing wilting and other injuries to vegetation,” said Dr. Bruce Fraedrich, director of the research laboratories at Bartlett Tree Experts.
Preventing and identifying damage from deicing salts is much easier when you know what to look for.
A lot of trees are affected by airborne salt kicked up by traffic. It settles on leaves, desiccating the tree. Some trees absorb the sodium and others suffer from root damage, caused by salt seeping into the soil. Species most susceptible to this type of damage are evergreens, including conifers, pines, spruce, and holly trees.
Professionals can identify damage by the wilting and dryness of leaves and other foliage, though symptoms are usually evident only after large masses of salt have accumulated. Damage to the soil can be spotted by noticing significant drooping, especially at the top of a tree, because salt inhibits absorption of water by the root system. Salt damage produces similar symptoms as drought. When caused by airborne salt (from vehicles), it usually occurs on the lower part of the tree, facing the street. Damaged trees also tend to have thinner leaves and often bloom later in the spring.
Other symptoms include: Stunted growth of foliage; browning of foliage; thinning of branch tips; premature fall colouration and defoliation; and dead branches. Severe cases often lead to insect infestation.
Damage is hard to prevent. Winter weather complicates efforts to help trees as there is no way to wash off salt. To counter the inevitability of salt damage, start by planting trees tolerant to salt (such as birch, oak, or juniper) near the road and driveway. Beyond that, monitor plants to ensure their overall health, keep trees well watered and use gypsum (calcium sulfate) to help counteract salt in the root system. A certified arborist can also help keep trees healthy year-round so they are less susceptible to winter issues like salt damage.
Several other measures can be taken to reduce the risk of damage: Divert salt sources from trees by erecting barriers of burlap or wood; lay down mulch to prevent seepage; and water thoroughly during dry periods. These preventative measures can decrease the chances of trees experiencing heavy damage.
Unfortunately roadside trees are likely to experience the most damage due to deicing materials, but by staying aware of the cause and solutions, arborists can help property owners prevent many long-term problems.
Bartlett Tree Experts
RRC #4037
RRC #4037
